Scoring blade and method for bone cement removal from intramedullary canal

ABSTRACT

An osteotome blade that is optimized for cutting and removal of bone cement such as from an intramedullary canal during revision surgery. The blade may have a body and a tip, wherein the body cross-section and tip are trough-shaped and the tip has a swept-back configuration. Further away from the cutting region, the blade may have a transition region and a hub suitable to be grasped in a power tool. There may also be provided a scoring blade, and a method may comprise scoring grooves into bone cement using the scoring blade, followed by removal of bone cement using the cement removal blade.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a Continuation-in-part Pat. Applications ofU.S. Serial No.17/699,831 filed Mar. 21, 2022, which claims priority toU.S. Provisional Patent Application Serial No. 63/164,915 filed Mar. 23,2021; U.S. Serial Number 17/699,831 is also a Continuation-in-Partpatent application of U.S. Serial No. 16/826,392 filed Mar. 23, 2020,now U.S. Pat. No.11,364,038 issued Jun. 21, 2022, which is aContinuation-in-Part of U.S. Serial Number 15/369,839 filed Dec. 5,2016, now U.S. Pat. No.10,595,879 issued Mar. 24, 2020. Reference isalso made to U.S. Serial No. 17/402,511, filed Aug. 14, 2021, whichclaims the benefit of U.S. Serial No. 63/066,089, filed Aug. 14, 2020.All of these are incorporated herein by reference in their entireties.

FIELD OF THE INVENTION

Embodiments of the invention pertain to cutting tools and orthopedicsurgery.

BACKGROUND

In orthopedic surgery it has historically been a difficult task to cutthrough bone cement that already exists in the body of the patient, suchas when performing a revision of a previous surgery at the same site.Bone cement typically comprises Polymethyl Methacrylate (PMMA) and is avery tough material that is not easily cut.

One method currently used to remove bone cement is the manual osteotome,or bone chisel, which is used in combination with a hammer to manuallychisel out the bone cement piece by piece. This is a very slow andlaborious process.

Another method is an ultrasonic device (for example Orthofix’s Oscar™system) fitted with various blades. The frequency of the bladevibrations is matched to the natural frequency of the bone cement. Thisproduces heat which causes the softening and/or melting of the bonecement, which allows the cement to be scooped and scraped out of bonecavities and off of bone surfaces. This is a slow and messy process thatalso produces noxious odors.

There are also various types of hooks, scrapers, and reamers that areused to try to remove bone cement. None of these methods is fast or easyto use. Accordingly, improvements are still desirable, especially with aview toward reducing the duration of surgery.

SUMMARY

In an embodiment of the invention, there may be provided a blade forcutting, the blade comprising: a tip, the tip having a tip thicknessmeasured perpendicular to a local surface of the blade; and a body,proceeding proximally from the tip, the body having a body widthdimension; wherein the body and the tip both extend generally along aproximal-distal direction, wherein the tip is trough-shaped having a tipconcave surface and an opposed tip convex surface, wherein the tip has atip cross-section, taken perpendicular to the proximal-distal direction,wherein, the tip cross-section has a concave surface that has, at somelocation, a tip internal radius of curvature that is a smallest radiusof curvature of the concave surface, wherein the tip cross-section canbe enveloped by a minimum tip enveloping rectangle that is a smallestrectangle that can enclose the tip cross-section, wherein the minimumtip enveloping rectangle has a tip section width dimension and a tipsection height dimension and has a tip aspect ratio that is a ratio ofthe tip section width dimension to the tip section height dimension,wherein the tip aspect ratio ranges from 1.0 to 3.5, wherein the tipinternal radius of curvature is between 2% and 40% of the body widthdimension, wherein the tip internal radius of curvature is approximately0.05 to 6.25 times the tip thickness, wherein when viewed from above theconcave surface, the tip has a swept-back configuration, and wherein thetip has a distal edge having a suitable sharpness and hardness to cut amaterial of interest. Furthermore, the body may be continuous with atransition region and a hub that is suitable to be gripped in a chuck ofa power instrument.

In an embodiment of the invention, there may be provided a method ofcutting bone cement comprising providing the described blade andrepeatedly striking the bone cement suitably to cut it.

In an embodiment of the invention, there may be provided a blade for usein cutting, the blade comprising: a guidance portion; a cutting portionthat is continuous with the guidance portion; a transition portion thatis continuous with the cutting portion; and a gripping portion that iscontinuous with the transition portion, wherein the blade has alongitudinal axis, wherein the cutting portion is planar having acutting portion planar surface facing in an upward direction and has atleast one cutting edge that is adapted for cutting, wherein the grippingportion has an upward-facing surface facing generally in the upwarddirection and the upward-facing surface does not entirely lie in asingle plane, and wherein the transition portion has a three-dimensionalsurface transitioning between the cutting portion and the grippingportion, wherein the guidance portion comprises edges that are lesssharp than the cutting edge of the cutting portion..

In an embodiment of the invention, there may be provided a method ofcutting bone cement comprising providing the described scoring blade andrepeatedly striking the bone cement suitably to cut an axial score intothe bone cement. In an embodiment, such scoring may be followed bycutting the material remaining between score marks using a differentblade that is suited for cutting or chipping away the remaining bonecement.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

The patent or application file contains at least one drawing executed incolor. Copies of this patent or patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee. Embodiments of the invention are further describedbut are in no way limited by the following illustrations.

FIG. 1A is an illustration of a typical femoral component of a hipreplacement, implanted in a femur. FIG. 1B shows the femoral componentremoved from the femur, also showing bone cement remaining in theintramedullary canal of the femur. FIG. 1C shows bone cement beingremoved from the intramedullary canal using an embodiment of theinvention.

FIG. 2A is a three-dimensional perspective view of a blade of anembodiment of the invention. FIG. 2B is a sectional view of FIG. 2A.FIG. 2C is a further sectional view of FIG. 2A.

FIG. 3A is a top view of the blade of FIG. 2A. FIG. 3B is a side view ofthe same blade.

FIG. 4 is a layout of a flat shape that can be bent or formed into theblade of FIG. 2A.

FIGS. 5A-5F show various possible shapes of the tip of the blade.

FIG. 6A shows a three-dimensional perspective view of the tip and aportion of the body of a blade of an embodiment of the invention. FIG.6B is a corresponding top view. FIG. 6C is FIG. 6B with, superimposed, asemicircle and two semi-ellipses. FIGS. 6D-6H show variouscross-sections through the tip.

FIG. 7A is a cross-section of FIG. 2A showing the bevel angle of thecutting edge of the blade. FIG. 7B illustrates possible locations ofgrinding of the cutting edge of the blade.

FIG. 8A illustrates the blade and its tip, particularly the tapering ofthe region that is ground or sharpened. FIGS. 8B and 8C illustratepossible details of the region that is ground.

FIG. 9A illustrates the hub of the blade. FIG. 9B illustrates across-section of the hub of FIG. 9A.

FIG. 10A is a cross-section of the hub illustrating an included angleand the minimum enveloping rectangle. FIG. 10B (like FIG. 2C) is asectional view of the body of the blade.

FIG. 11 shows the blade together with its splash guard.

FIG. 12 illustrates various shapes of the tip of the blade that weretested during the configuration survey portion of the testing.

FIG. 13 is a pictorial summary of the various stages of testing alongwith trends observed.

FIG. 14 shows a blade, of an embodiment of the invention, being tested.

FIGS. 15A and 15B show embodiments of the invention in which the body ofthe blade has a longitudinal path that is other than straight.

FIG. 16 shows an embodiment of the invention in which the tip includes abend or angle.

FIG. 17A is a three-dimensional perspective view of a scoring blade.FIG. 17B is a top view of the same blade. FIG. 17C illustrates that thecutting edge of the scoring blade forming a defined angle with respectto the long axis of the blade 2010. FIG. 17D is a side view of the sameblade. FIG. 17E shows a blade in which the guidance region issymmetrically located. FIG. 17F shows a blade in which the guidanceregion is offset from the longitudinal axis of the blade. FIG. 17G showsa scoring blade in which the guidance region has a tip that issharpened.

FIG. 18A shows the use of the axial scoring blade at the beginning of ascoring cut. FIG. 18B shows the use of the axial scoring blade during ascoring cut. FIG. 18C is a sectional view of FIG. 18B.

FIG. 19A shows the use of the Cement Removal Blade after the creation ofscoring cuts. FIG. 19B is a sectional view of FIG. 19A.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In an embodiment of the invention, there is provided a blade 10 that issuitable to work with a powered handpiece or instrument such as anosteotome that actuates the blade 10 forward, or back and forth manytimes per second. The power stroke on each actuation, which is typicallythe forward direction, is the direction that causes the blade 10 to cut.In such usage, each actuation of the blade 10 causes an impact to thebone cement or other material with which the blade 10 is in contact,suitably to cut or chip the bone cement or other material.

In embodiments of the invention, the blade 10 may be suitable to be usedin an intramedullary canal of a bone, such as the intramedullary canalof a femur, to remove bone cement that had been placed there during anearlier surgery. This is illustrated in FIGS. 1A, 1B and 1C. FIG. 1A atypical femoral component of a hip replacement, as it is normallyimplanted in a femur. FIG. 1B shows the femoral component removed fromthe femur, as during revision surgery. FIG. 1B also shows bone cementremaining in the intramedullary canal of the femur. FIG. 1C shows bonecement being removed from the intramedullary canal using an embodimentof the invention.

The intermedullary canal of an adult human femur is usually less than 25mm inside diameter in the region of the femur that is occupied by theshaft of a femoral implant for hip replacement. Therefore, in order toremove bone cement, cutting blades need to be able work in space-limitedopenings that are of a generally cylindrical shape, often in spaces thathave an inside diameter of approximately 12-18 mm. So, the width ofblade 10 may be such as to be capable of fitting in spaces of thosedimensions, while also being able to effectively cut and remove materialsuch as bone cement.

Referring now to FIG. 2A, there is shown an overall view of a blade 10of an embodiment of the invention. The blade 10 may have a longitudinaldirection that is a proximal-distal direction. The blade 10 may comprisein sequence, a tip 20, a body 30, a transition region 40, and a hub 50.These components are listed proceeding in sequence from distal (farthestfrom the hub 50, closest to the patient) to proximal (the hub 50,closest to the user).

In general, the performance of the blade for cutting bone cement may beinfluenced by the following geometric parameters, which are discussedherein:

-   Blade Thickness T-   Radius of curvature “R” at bottom or vertex of the trough-   Body trough included Angle “A” of the trough, or, more generally,    the aspect ratio of the minimum enveloping rectangle of the body-   Sweep-back properties-   Tip shape frontal geometry in plan view, such as frontal radius Rf-   Angle “E” (angle of the bevel at the cutting edge)-   Cutting edge location relative to thickness of tip-   Radius of Sharpness of the tip (Rt in FIG. 7A)

In regard to blade thickness of blade 10, the blade 10 may, asillustrated, have a blade thickness T, which may be substantiallyconstant throughout the blade 10. Such construction may be consistentwith manufacturing the blade starting from sheet material and laterforming the blade into a three-dimensional shape such as by stamping orbending. The blade thickness T may be 0.042 inch, or more generally inthe range of 0.010 inch to 0.125 inch. Alternatively, the bladethickness could be tapered or of varying thickness. The width of theblade 10 may be 0.2 inches to 1.0 inches.

Geometric Details of Trough of Body

As illustrated in FIG. 2 , in embodiments of the invention, the body 30of the blade 10 may have a cross-sectional shape that is generally atrough shape having a concave (upward) surface and an opposed convex(downward) surface. In some embodiments, as illustrated in FIG. 3 , thecross-sectional shape of the body may be a “rounded-V” shape with arounded bottom as seen in FIG. 2A and enlarged in FIG. 2B. In such asituation, the cross-sectional shape may comprise, in succession, afirst straight leg body portion, a curved body portion that iscontinuous with the first straight leg body portion, and a secondstraight leg body portion that is continuous with the curved bodyportion. This internal radius of curvature of the curved body portioncan have desired relationships with other geometric parameters of theblade 10, as described elsewhere herein. The first and second straightleg body portions may define an included angle “A” (body trough includedangle) between them. Exemplary values of the included angle arediscussed elsewhere herein.

More generally, the body cross-section does not have to be exactly arounded-V shape, but still it may be trough-shaped and have a concavesurface. Even though a generalized shape might not have any straightsegment, the shape still may have, at some location, a body internalradius “R” that is a minimum radius of curvature of the concave surfaceof the body cross-section. As before, this internal radius of curvaturecan have desired relationships with other geometric parameters of theblade 10, as described elsewhere herein.

Continuing in regard to this more generalized shape, the cross-sectionmay be described by a minimum body enveloping rectangle that is thesmallest rectangle that can enclose the body cross-section. This isillustrated in FIGS. 2C and 10B. As can be seen, the minimum bodyenveloping rectangle is tangent to the concave surface of the body atthe underside of the body, and elsewhere the rectangle touches variouscorners of the edges of the body cross-section. The minimum bodyenveloping rectangle has a body width dimension and a body heightdimension. From these two dimensions can be calculated a body aspectratio that is a ratio of the body width dimension to the body heightdimension. This aspect ratio can convey somewhat similar information asthe included angle that is defined for a rounded-V cross-section, butthe aspect ratio is applicable in generalized situations whether or notthe cross-sectional shape comprises any straight-line segments.Exemplary values of this aspect ratio parameter are given elsewhereherein.

It can be noted that as illustrated, the tip 20 and the body 30 may havesubstantially identical cross-section, and one difference between thetip 20 and the body 30 lies in the external shape of the tip 20. Inparticular, the tip 20, when viewed in plan view, may have a contoureddistal end, which signifies the absence of material. Also, an edge ofthe tip 20 may have a beveled or tapered sharp edge suitable forcutting. As shown in FIG. 7A, the tip radius of the cutting edge may beless than 0.01 inch. More generally, it is possible that thecross-sectional shape of the body 30 and the cross-sectional shape ofthe tip 20 of the blade 10 do not, in general, have to be the same aseach other. For example, there could be differences in parameters suchas angles, radii, and lengths of sides, for example.

In regard to trough radius, the trough radius “R” in FIG. 2B of the“rounded-V” portion of the blade 10, as measured at the inside (concave)surface of the bend, may be between 0.02 inches and 0.20 inches. This isbelieved to correspond to the best cutting action of the blade 10 onbone cement. More specifically, a typical dimensional value of thatradius may be 0.03 inch or 0.09 inch. A further way of describing thismay be that the ratio of trough radius to blade material thickness maybe in the range of 0.15 to 6.0, or, more specifically, between 0.5 and4.0. The body internal radius of curvature may be between approximately0.05 to 6.25, or between 0.2 to 4, times the body thickness. The bodyinternal radius of curvature may be between 2% and 40%, or between 5%and 25%, of the body width dimension.

In regard to trough included angle, the trough included angle “A” inFIG. 2C of the “rounded-V” tip cutting portion of the blade 10 may bebetween 40 and 140 degrees. This is believed to be the range of anglesthat provide good cutting action. A preferred value of the troughincluded angle would be approximately 80 degrees.

For situations in which the geometry is described by the aspect ratio ofthe minimum body enveloping rectangle, it is found that good cuttingresults are obtained with a body aspect ratio in the range of 1.0 to3.5. Of course, the choice of a body aspect ratio or an included anglecan also be influenced by the geometry of the intramedullary canal orother aspects of the surgical site for which use is intended.

Geometric Details of the Tip

The tip 20 may be the portion of the blade 10 that impacts the bonecement or other material at the surgical site and does the actualcutting. In embodiments of the invention, there may in general be somekind of tapering or reducing of dimensions at or near the tip, orsweeping-back, so that impact or compressive force carried by the body30 of the blade 10 is applied to a working area that is smaller than thecross-sectional area of the body 30 itself.

In embodiments of the invention, a typical way of manufacturing theblade 10 is by first producing a flat blank that may already containsome of the overall geometric features of the eventual blade 10. Such aflat blank is illustrated in FIG. 4 . The flat blank may be of uniformthickness. In a later manufacturing step, the flat blank may be bent orstamped or deformed so as to produce the final three-dimensional blade10. Accordingly, one way of describing the plan view shape of the tip isby describing the shape of a flat blank that may be present in anintermediate step in the manufacturing process.

One possible geometry of the tip 20 is that, when the blade 10 is viewedfrom above (which may be referred to as plan view) in the flat sheetmetal state, prior to being stamped or bent or deformed into the shapethat created the trough geometry, the tip 20 may have a distal end thatis a semicircle whose diameter is the width of the flat blank. Inembodiments of the invention, the radius “T” of the tip 20, if the blade10 is in a flat condition, before it is bent, formed, or machined intoits eventual trough shape, may be between 0.05 and 0.5 inches.

In still further embodiments, the flat state of the blade 10 may haveany of the shapes illustrated in FIGS. 5A-5F. For example, it ispossible that, in plan view, the tip 20, could be semi-hexagonal orsemi-octagonal as illustrated in FIG. 5C. In addition to thesemi-hexagonal and semi-octagonal tip configurations, still other tipconfigurations are possible using polygons of any other desired numberof sides. Such polygons could be portions of regular polygons (all sidesand all angles being equal) as illustrated, or alternatively could beany other polygonal shape. The shape could alternatively be acontinuously curved shape. There could alternatively be various othermulti sided geometries that approximate the geometries shown.

Another possible way of describing the shape of the tip 20 of the blade10 is its shape in plan view after the bending or forming into thethree-dimensional shape of the blade. This is shown in FIGS. 6B, 6C.

FIG. 6B illustrates that the tip may be characterized by a minimumenveloping rectangle in plan (top) view. The tip 20 for purposes of thisrectangle may be considered to begin when the profile departs from aconstant-width body 30. This minimum enveloping rectangle of tip (topview) may have a tip width and a tip length. The ratio of these is anindicator of to what extent the tip is “swept back.” The ratio tiplength / tip width may be chosen to be between 0.1 and 2, morepreferably between 0.3 and 1.2.

As a point of comparison, shown in FIG. 6C, it is possible to envision ahypothetical semicircle whose diameter equals the width of the blade(after the bending) in plan view, and which is tangent to thedistal-most point of the tip 20 of the blade 10. (Such a semicirclemight not exactly correspond to the semicircular end of the flat blankprior to bending, but it would be similar.) Similar to thejust-described semicircle, it is possible to envision two hypotheticalellipses that also are tangent to the distal-most point of the tip 20 ofthe blade 10. Each of these ellipses may be centered on the midplane ofthe blade 10. Each of these ellipses may have a lateral semi-axis thatis equal to half of the width dimension of the body 30 of the blade 10.For one of these ellipses, the proximal-distal semi-axis may beone-quarter of the blade width dimension. For the other of theseellipses, the proximal-distal semi-axis may be the blade widthdimension. In an embodiment of the invention, the distal edge of theblade 10, in plan view, may have a shape that lies between these twoellipses.

A common effect of these various configurations of the tip is that thethree-dimensional shape of the tip becomes “swept back” such that theportion of the tip that actually contacts the subject material such asbone cement has a smaller width than the width of the body 30 in planview, and has a smaller cross-sectional area than the body 30 has. Asdescribed elsewhere herein, it is believed that this contributes toconcentrating the impact or compressive force into a smaller area forimproved cutting, and also contributes to a sort of stability such thatthe tip 20 does not wander away from the working area. It is believedthat there are optimum design parameters to achieve this, as describedelsewhere herein.

It is further possible to characterize the tip 20 as having across-sectional shape, which is shown in FIGS. 6D-6H for five differentsectioning locations starting with the section in FIG. 6D being closestto the tip and sections in FIGS. 6E, 6F, 6G, 6H being progressivelyfurther away from the tip. At each of these sections there may be atrough radius of curvature and, if straight segments exist at thatsection, an included angle. At each section there may be a minimumenveloping rectangle, which may have a tip section width dimension and atip section height dimension, as illustrated in FIGS. 6D-6H. At eachsection, a tip section aspect ratio may be defined as a ratio of the tipsection width dimension to the tip section height dimension. The tipaspect ratio may range from 1.0 to 3.5. The tip aspect ratio may varydepending on where in the tip a particular section is taken. As can beseen, in some places the section may be crescent-shaped while in otherplaces shape of the tip section may be more similar to the shape of thesection through the body 30. The trough internal radius of curvature ofthe tip may be identical to that of the body, or it may be different.The tip internal radius of curvature may be between 2% and 40%, orbetween 5% and 25%, of the body width dimension. The tip internal radiusof curvature may be between approximately 0.05 to 6.25, or between 0.2to 4, times the tip thickness. The included angle of various sections ofthe tip, if such sections have straight-line segments that can define anincluded angle, may be identical to that of the body 30 or may bedifferent. The tip aspect ratio may be identical to that of the body 30,or may be different.

Cutting Edge Details of the Tip

Embodiments of the invention may comprise a sharp distal edge suitableto cut bone cement or other material. The existence of a sharp distaledge may contrast, first of all, with the situation for certainultrasonic tools which macroscopically have a similar distal end shape.The ultrasonic tools do not actually cut or chip bone cement, but ratherthey transmit vibrations to the bone cement, with the vibrations beingtuned to the natural frequency of the bone cement through the blade, soas to generate heat and ultimately soften or melt the bone cement sothat the tool can be pushed through the bone cement.

In embodiments of the invention, the tip 20 may have a cutting edgeradius of no more than 0.010 inch. More generally, such cutting edge maybe as sharp as is practically possible, and may be formed by grinding,for example.

In regard to location of the cutting edge with respect to the thicknessof the blade 10, it is possible that the cutting edge can be either onthe top surface of the blade, the bottom surface of the blade, orbetween the bottom and top surfaces of the blade. In general, thecutting edge may be adjacent to the concave surface of the tip 20(referred to as the top side), or may be adjacent to the convex surfaceof the tip 20 (referred to as the bottom side), or may be in between. Itis believed that, for good removal of bone cement, it is helpful if thecutting edge is directly at the convex (bottom) surface of the tip 20.This is referred to as top grind because if the sharp edge is formed bygrinding, as is typically done, the removal of material by grindingwould occur on the top (concave) surface of the blade 10. This is theconfiguration that is illustrated in FIGS. 6 and 7A. For this purposethe cutting edge may be located at the convex (bottom) surface of thetip 20 or within 10% of the body thickness thereof.

Referring now to FIG. 7A, there is shown a longitudinal cross section ofthe tip from FIG. 2A. In this figure, there is shown the bevel angle oredge angle “E” to which is the angle the cutting edge is beveled. FIG.7B also shows these angles in profile -including “top”, “bottom” and“both” top and bottom (center) cutting angles. This angle “E” may bechosen to be between 5 and 60 degrees for “top” and “bottom” cuttingedges. It is illustrated as 25 degrees. In the case of a blade 10 thatis beveled on both top (concave) and bottom (convex) surfaces, theincluded angle “E” between the beveled edges may be chosen to be between10 and 120 degrees.

For this illustrated configuration, in an embodiment of the invention,the bottommost portion of the tip 20 may lie on the same plane that runsalong the body 30 of the blade 10. During use for removal of bonecement, this feature allows the blade 10 to slide or contact right upagainst the bone (such as the internal surface of the intramedullarycanal) and parallel to the bone while the blade 10 is cutting into thebone cement. If the cutting edge were at the top (concave) surface ofthe blade could not run right up against the bone and still be parallelto the bone, and its cut would have to be at least the blade thicknessaway from the bone. If the cutting edge were located in the middle ofthe thickness of the blade material, or somewhere between the top andbottom surfaces, this also would create the situation where the cuttingedge would be some distance away from the bone when the blade isparallel to the bone. This ability for the blade to run parallel to thebone while running right up against the bone is believed to be importantwhen the blade 10 is removing bone cement in the intramedullary canal,which is a common area of bone cement use. In the intramedullary canalsthere is limited room to angle the blade 10 to achieve a cut against thebone. So, in order to remove all the bone cement, which is a desiredoutcome, it is helpful for the external (convex) surface of the blade 10to slide or contact right up against the bone (such as the internalsurface of the intramedullary canal) to remove all the bone cement,i.e., for the cutting edge to coincide with the bottom (convex) surfaceof the tip of the blade.

An embodiment of the invention has the cutting edge shaped into the tip20 from the top side as shown in FIGS. 7A-8C. This may be formed bygrinding. The grinding or machining of the cutting-edge angle “E” mayentail following the curve or geometry of the blade tip around its edgesuntil they become tangent or coincident with the sides of the bladebody. This grinding of the edge may also include a tapering off of theblade edge as it transitions from the tip to the body.

The tapering of the edge of the blade is illustrated in FIGS. 7A-8C. Inembodiments of the invention, it is further possible that the blade edgeangle “E” may also vary as a function of position along the tip edge toachieve a more desirable cutting action. For example, it may bedesirable to have a larger Edge Angle “E” at the base of the trough anda smaller Edge Angle “E” as you move away from the trough up the sidesof the tip. FIGS. 8B and 8C show a view of one leg of the “rounded-V” ofthe tip.

The blade 10, or at least its tip, may have a hardness that is suitableto cut the material of interest such as bone cement. For example, thehardness may be HRC 35 (Hardness Rockwell C of 35) or harder. The blade10 may be made of or may comprise stainless steel, for example, or othersuitable metal.

Transition Region and Hub

Proceeding further proximally along the proximal-distal direction ofblade 10, there may be a transition region 40 that is continuous withbody 30. Still further proximally, there may be a hub 50 that iscontinuous with transition region 40. The hub 50 may be suitable to begrasped by a tool such as a pneumatically or electrically operated powertool, or may be suitable to be struck with a hammer. There may begeometric differences between the hub 50 and the body 30, which may makeit appropriate to provide a transition region 40.

In an embodiment, the hub 50 may be such that, in a cross-section of thehub 50 taken perpendicular to the proximal-distal direction, the hub 50has a hub cross-section, and the hub cross-section can be enveloped by aminimum hub enveloping rectangle that is a smallest rectangle that canenclose the hub cross-section. Similar to the previously defined minimumenclosing rectangle for the body, the minimum hub enveloping rectangleis tangent to the concave surface of the hub at the underside of thehub, and elsewhere the rectangle touches various corners of the edges ofthe hub cross-section. This minimum hub enveloping rectangle may have ahub width dimension and a hub height dimension, and a hub aspect ratiocan be calculated as a ratio of the hub width dimension to the hubheight dimension. In embodiments, the hub aspect ratio may range from0.1 to 10.

In embodiments, the hub aspect ratio could be different from the bodyaspect ratio, which is what is illustrated in FIG. 9 . Alternatively, ifdesired, the hub aspect ratio and the body aspect ratio could be equalto each other. The hub bend radius or minimum radius of curvature couldbe the same as the body bend radius or minimum radius of curvature.Alternatively, these quantities could be different from each other ifdesired.

In embodiments, the hub 50 width dimension may be greater than the bodywidth dimension. For example, this may provide increased structuralstrength of the blade 10 near where the blade is gripped by a powertool. Such space for strength and gripping features might be unavailablefor the portion of the body 30 of the blade 10 that is intended to fitwithin the intramedullary canal.

In embodiments, the hub 50 may comprise holes or other geometricfeatures for interfacing with a driver tool or other components. In FIG.9 , hole 60A may be suitable for interfacing with a driver tool. Holes60B and 60C may be suitable for interfacing with a splash guard. Such asplash guard is illustrated in FIG. 11 .

It can be understood that, if desired, still other interfaceconfigurations may be designed for the hub 50, as may be desired for aparticular driving tool that may hold blade 10.

In embodiments, the blade 10 may have dimensions appropriate for fittinginside typical dimensions of an intramedullary canal that contains bonecement needing to be removed during revision surgery. For example, thewidth dimension of the body 30 may be in the range of 0.2 inch to 1.0inch. The length of the body 30 may be in the range of 1.0 inch to 18inch.

The blade 10 may comprise metal such as stainless steel and may have athickness suitable so that the blade can withstand a compressive orimpact force along the proximal-distal direction of at least 10 Nwithout buckling, or at least 50 N.

Embodiments of the invention are further described, but are in no waylimited, by the following Examples. A series of tests was performed tooptimize the design of the blade, by experimenting with actual cuttingof materials including bone cement.

Example 1

Initially, a first round of blade testing was a configuration survey, inwhich we tested various widely varying geometries (see FIG. 12 ) to seewhat overall geometric category performed best. We tested flat bladeswith flat cutting edges (like a conventional chisel), round edges, andpointed triangular cutting edges. We tested various widths of theseblades, including 4 mm and 6 mm widths of several blade designs. (Thisis smaller than the width of the blade 10 described elsewhere herein.)We tested concave blades having rounded and flat cutting edges. Wetested “rounded-V” shaped blades with flat and sloped edges. All bladestested had top ground edges.

From this testing, we found that the sloped (swept back) “rounded-V”shaped blades cut significantly better than the various other blades(see Table 1). We determined that the pressure concentration at thepoint of the swept-back “rounded-V” allowed the blade to penetrate andremove the tough bone cement especially well. The “rounded-V” shapeallowed the cutting to continue as a slicing action through the bonecement. The shape of the swept-back “rounded-V” provided structuralsupport for the cutting edge while keeping the cutting edge rigid duringthe cutting process. It is believed, although it is not wished to belimited to this explanation, that a greater “swept back” blade designthat produces a more pronounced pressure concentration at the point ofthe blade tip 20 will impart more local pressure to the surface of thebone or bone cement because the blade force is concentrated onto asmaller surface area. A blade design having small or no “sweep back”(such as, in the extreme, a conventional chisel) will impart less localpressure because the blade force is spread out over a larger surfacearea of the material it is cutting. These findings are summarized inTable 1.

TABLE 1 Blade Results Score Flat Edge - 4 mm wide Dug down into cementwithout creating chips 3 Flat Edge - 6 mm wide Difficulty in getting itto dig into cement 2 Round Edge - 6 mm Started fair and became boggeddown quickly 3 Triangular - 6 mm Started good and became bogged downquickly 4 Concave - 4 mm Slow cutting with minimal chipping 4 Concave -6 mm Very slow cutting with no chipping 3 V bend - Straight 4 mm Startedgood, became slower, minimal chipping 4 V bend - Straight 6 mm Startedgood, became slower, moderate chipping 3 V bend - Slanted 4 mm Goodcutting, much faster than others, good chipping 7 V bend - Slanted 6 mmGood cutting, a little slower than 4 mm V bend slanted, good chipping 6

As a result of this configuration survey, we selected and focused onconcave trough-shaped blades that had some slanted sweep-back, and wesought to further optimize that category of blade geometry. For thisoptimization study, we designed a number of variations of this design inorder to find an optimum cement removal blade (see Table 2 and FIG. 13). For this optimization study, the blades were made by cutting orforming a Flat Blank from sheet metal, and then the Flat Blank was bentor stamped to make it into a three-dimensional rounded-V trough shape.For all of the experiments in this optimization study, we used the sameFlat Blank and we only varied the details (included angle, bend radius)of the rounded-V shape into which the Flat blank was bent or stamped.For the blades tested in this group of experiments, the Flat Blankconfiguration of the blades, prior to bending, was such that the tip atthe distal end was shaped as a semicircle having a diameter equal to theblade width in the Flat Blank condition. All of the experimental bladesin this group of tests had the same width of the Flat Blank of theblade. The parameters that we varied were the included angle (A) and theBend Radius (R). The included angle was varied as follows: 80, 100, and120 degrees. The Bend Radius was varied as follows: 0.03 inch, 0.09inch. We decided on combinations of these variables that we thoughtwould give us the best opportunity of success. Due to resources, webuilt and tested only the blades having 0.09 inch Bend Radius (themiddle value of bend radius) in the three different “V” angles, and alsoone other case in which the bend radius was 0.03 inch.

All of these blades were ground to a cutting edge that had a 25 degreetaper angle at the outer (convex) surface of the blade. All of theblades were tested with the same instrument on the same type of bonecement block (see FIG. 8 for test setup). All blades were tested at 3600strokes per minute using a Palix Medical LLC VersaDriver™ PneumaticOsteotome. Results for each blade were judged subjectively by the designengineer who was performing the test, and an overall score wasdetermined by that engineer. The tests were performed twice, and Test 1and Test 2 were performed by different engineers in order to obtain twodifferent independent opinions about the subjective test results.Results were evaluated by a score and a description of the cuttingresult. The score was a relative rating of the tested blade’s cuttingability compared to a hypothetical ideal blade that would cut with idealcontrol and speed. The purpose for having two different engineersevaluate the blades was to get two different independent opinions.

The last entry in the table, CRB-X, somewhat resembled the CRB-02 designbut it had a slightly sharper included angle “A” at 60 degrees, and itsbend radius of 0.03 inch also was sharper than that of CRB-02. It wasfound that this blade provided the fastest cutting speed of all theblades, but that blade was very difficult to control and repeatedlywandered away from the desired path.

TABLE 2 Summary of tests of rounded-V shaped blades Test 1 (byEngineer 1) Blade Trough angle Bend radius Results Score CRB-02 80 0.09Cut really well. Takes out lots of small chips quickly. Great control10/10 CRB-04 100 0.09 OK. Digs in a little and wants to take out largerchips. Less control than CRB-02 7/10 CRB-06 120 0.09 Really digs intothe bone block. Slow cutting and chips are large. Least control 4/10Test 2 (by Engineer 2) Blade Trough angle Bend radius Results ScoreCRB-02 80 0.09 Very controlled. Fast cutting 10/10 CRB-04 100 0.09Slower than CRB-02, digs in more before separation of chips. Chipslarger than CRB-02. 8/10 CRB-06 120 0.09 Slower to create chips. Chipsbigger than CRB-02 and CrB-04. Bogs down during cutting. 5/10 CRB-X 600.03 Fastest cutting speed of all the blades, but very difficult tocontrol; wanders

It can be seen in Table 2 that Blade design CRB-02 was preferable. Allof results from both phases of the testing (both the configurationsurvey and the optimization study) are summarized in FIG. 13 .

FIG. 14 is a photograph showing the CRB-02 prototype blade cutting bonecement during testing. For this testing, the axial force on the bladewas provided by Palix Medical LLC’s Versa Driver Pneumatic Osteotome.This is the blade that was judged to give the best performance of all ofthe blades that were tested. It can be seen that the blade chips away atthe bone cement resulting in the creation of small chips, which is whatis considered desirable for the intended application.

Example 2

Several orthopedic surgeons have used the described blade both in alaboratory setting and in surgery. All of them had commented, prior totrying the described blade, that they were reluctant to use a poweredinstrument to remove bone cement in the intramedullary canal of thefemur, because if the tool were to wander from its intended locationthere would be a chance of the tool perforating the femur and causingsignificant damage.

One orthopedic surgeon, who had not yet used the blade of an embodimentof the invention, planned a very difficult revision surgery in which hehad to remove a hip implant having an unusually long femoral stem thatwas implanted into the femur. He planned that several of his instrumentsuppliers would bring a wide variety of equipment into the surgery.After trying all of the available instruments during the surgery withoutsuccess, he tried a blade of an embodiment of the invention. He startedusing the blade in a very conservative manner, but soon was using itunder full power and was very confident in its use. In 5 minutes ofsurgical time using a blade of an embodiment of the invention, hecompleted the work, and he estimated that it would have taken himanother two hours of surgical time to do the same work manually. Heplans to use the blade frequently, because of the controllability thatit provides, along with its cutting efficiency.

An embodiment of the invention can be a method of cutting bone cement,comprising providing a blade of an embodiment of the invention, andcausing the blade to repeatedly strike the target bone cement suitablyto cut or remove the bone cement.

Scoring Blade

In an embodiment of the invention, there may be provided a blade 2010 asillustrated in FIGS. 17A-17G. Such a blade may be referred to as ascoring blade and may be suitable to create axial cuts such as slots orgrooves in bone cement that may be present on internal surfaces of awall of an intramedullary canal.

Referring now to FIG. 17A, blade 2010 may comprise in sequence, aguidance region 2015, a cutting region 2030, a transition region 2040,and a hub 2050. These components are listed proceeding in sequence fromdistal (guidance region 2015, being closest to the patient) to proximal(the hub 2050, being closest to the user). The blade 2010 may have alongitudinal direction 2012 that is a proximal-distal direction. In anembodiment, guidance tip 2015 and cutting region 2030 may be part of aflat planar portion of the blade 2010.

The blade 2010 may, as illustrated in FIG. 17A, have a blade thicknessT, which may be substantially constant throughout the blade 2010. Suchconstruction may be consistent with manufacturing the blade 2010starting from constant-thickness sheet material and later forming theblade into a three-dimensional shape such as by stamping or bending. Theblade thickness T of blade 2010 may be 0.042 inch, or more generally inthe range of 0.010 inch to 0.125 inch. Alternatively, the bladethickness could be tapered or of varying thickness.

Hub 2050 may have a geometry that is non-planar. Hub 2050 may have across-sectional shape, in a cross-section taken in a sectioning planethat is perpendicular to longitudinal axis 2012. As illustrated, hub2050 has a cross-sectional shape that is generally V-shaped, but withthe vertex of the V being less than fully sharp. In FIG. 17A, the vertexis shown as being a rounded vertex. Of course, the vertex could ifdesired be sharp. Hub 2050 may have a concave surface and a convexsurface opposed to the concave surface.

Hub 2050 may be suitable to be received in a chuck that is capable ofgripping the hub 2050 of blade 2010. The gripping action of a chuck ontoblade 2010 may be provided by any one or more of various elements thatcan urge or bear against respective surfaces of the hub 2050, or maysimply constrain the location of hub 2050 within a desired close range.The chuck could be part of a larger tool, which could be any of apneumatically powered tool, an electrically powered tool, or a hand-heldtool, or generally any kind of tool or instrument. Such a chuck and toolare illustrated in commonly assigned U.S. Pat. 10,595,879 and incommonly-assigned U.S. Pat. Application Serial No.17/402,511. It isstill further possible that chuck 2050 or an equivalent may be suitableto be struck on its proximal end with a hammer, mallet or similarinstrument, such as by having a flat surface that is generallyperpendicular to a longitudinal axis of the blade 2010. It is stillfurther possible that hub 2050 may be suitable to be struck on itsproximal end with a hammer, mallet or similar instrument, such as byhaving a flat surface that is generally perpendicular to a longitudinalaxis of the blade 2010. In such a situation, there might be no need toactually grip hub 2050 in a chuck.

Between hub 2050 and cutting region 2030 there may be a transitionportion 2040. A transition portion 2040 is further illustrated incommonly assigned U.S. Pat.10,595,879 and in commonly assigned U.S. Pat.Applicarion Serial No. 17/402,511. In the transition portion 2040 thatis nearest cutting region 2030, the transition portion 2040 may benearly flat. In the transition portion 2040 that is nearest hub 2050,the transition portion 2040 may have almost the same cross-section ashub 2050. In between, there can be transition surfaces that are smoothlycurving surfaces appropriate to achieving the desired geometrictransition. It is believed that the use of transition region 2040creates a situation where there is less of a stress concentration factorthan in a situation of abrupt geometric change.

In embodiments, the overall width of the cutting region 2030 of blade2010 may be 0.2 inches to 1.0 inches.

In an embodiment, the Scoring Blade 2010 may comprise a flat bladeportion that has a notch cut into its side or end, creating a smallcutting edge 2032 of a defined depth and also creating a guidance region2015 that extends beyond the cutting region 2030.

In regard to the guidance region 2015 and referring now to FIGS.17A-17G, a portion of the guidance region 2015 may have a guidance edge2016 that is generally parallel to the longitudinal direction 2012 ofblade 2010 or to the direction of motion of blade 2010 during a cuttingprocedure. During use, such guidance edge 2016 or guidance surface mayride on undisturbed bone cement that is deeper in the intramedullarycanal than already-scored bone cement associated with the score that isin progress.

In an embodiment, the guidance region 2015 or guidance edge 2016 mayhave at least some portion or surface that is not sharp and is notadapted for cutting. This may be a longitudinal surface that isgenerally parallel to the longitudinal direction 2012 of blade 2010. Forexample, it may be considered that all or at least a majority of theedges or surfaces of guidance region 2015 may be less sharp than thecutting edge 2032 of the cutting region. It may be considered that allor at least a majority of the edges or surfaces of guidance region 2015that are generally parallel to the longitudinal direction 2012 of blade2010 may be less sharp than the cutting edge 2032 of the cutting region.It may be considered that all or at least a majority of the edges orsurfaces of guidance region 2015 may have an edge radius of curvaturegreater than 0.002 inch. It may be considered that in general, forcutting, a cutting edge radius of curvature of 0.010 inch or greater isnot suitable for cutting. A cutting edge radius of curvature between0.010 inch and 0.002 inch is possibly suitable for cutting but notpreferred for cutting. A cutting edge radius of curvature of less than0.002 inch is preferable for cutting. In an embodiment, the distal-mostedge or surface of the guidance region 2015 may be not sharp or notadapted for cutting.

Guidance region 2015 may control the positioning of the cutting edge2032 for penetrating or cutting bone cement. As a result, the guidanceregion 2015 may bear against intact bone cement deeper into theintramedullary canal, while the cutting edge 2032 associated with thenotch cuts a generally axially-oriented groove into the bone cement.This gives the surgeon great control over how deep a cut is made intothe bone cement so as not to go so deep as to cut into the bone. The tipof the guidance region 2015 can be flat, chamfered, or rounded so itdoes not catch or dig into the bone or bone cement as it slides alongthe bone surface of the bone or bone cement.

Although the guidance edge 2016 is illustrated as being straight andgenerally parallel to the longitudinal direction 2012 of the blade 2010,the guidance edge 2016 also could have other shape if desired.

Referring now to FIGS. 17B and 17C, it is illustrated that the cuttingedge 2032 of the scoring blade 2010 may be generally straight and mayhave a defined angle with respect to the long axis of the blade 2010.This angle is labeled as θ in FIG. 17C. In FIG. 17D, the angle θ isillustrated as being less than 90 degrees, which may be referred to as aforward-sloping cutting edge 2032. During use, such an angle on thecutting edge 2032 can be expected to provide a force component acting onthe blade 2010 which would tend to urge the guidance edge 2016 upagainst the not-yet-disturbed bone cement surface that is located deeperin the intramedullary canal. This is believed to be a desirable featureas it will help to keep the depth of cut consistent. In FIGS. 17E-17F,it is shown that the cutting edge 2032 is perpendicular to thelongitudinal direction of blade 2010, in which case θ is 90 degrees. Itis also possible that the cutting edge 2032 could be sloped such that θis greater than 90 degrees, if desired. The cutting edge 2032 could alsobe shaped in various geometric shapes, such as curved, and it could besharp-edged or could be serrated, etc.

Referring now to FIG. 17E, in an embodiment, notches may be cut intoboth sides of the cutting region 2030 of blade 2010. The notch maydefine the cutting edge 2032, which has a width W. The depths, orwidths, of the notches could be equal on opposite sides of the cuttingregion 2030, as illustrated in FIG. 17B and FIG. 17E. Alternatively, asillustrated in FIG. 17F, the width of the notch could be different onthe two different sides of the blade, illustrated as W1 on one side ofthe blade 2010 and W2 on the other side of the blade 2010. The providingof two different cutting edge widths W1, W2 on opposite sides of theblade 2010 allows for cutting more or less deeply into the bone cement,depending on which edge of the blade 2010 is used for cutting, withoutremoving a blade 2010 from the power tool and replacing it with adifferently dimensioned blade 2010. This can be useful when bone cementhas different local thicknesses in different places in a particularpatient. It is illustrated in some illustrations that the notch width orinset distance on one side of the blade 2010 is identical to the notchwidth or inset distance on the other side of the blade. It also isillustrated in FIG. 17F that these two distances could be different fromeach other. In such a situation, the surgeon would have two optionsregarding how to use the blade 2010. Two different depths of cut wouldbe available to the surgeon, without a need to remove and replace theblade 2010 from a power tool. In order to change the depth of cut, thesurgeon could simply withdraw the blade from the intramedullary canal,re-orient the power tool including the blade 2010, and then re-insertthe blade 2010 into the intramedullary canal and perform scoring cutsusing the other edge of the blade 2010. This could be done for differentscoring cuts, or for different portions of a single scoring cut. This isillustrated in FIGS. 17E-17F for a cutting edge 2032 that is generallyperpendicular to the long axis 2012 of blade 2010.

In embodiments, the cutting edge 2032 could be Center Ground, TopGround, or Bottom Ground, or some other geometric configuration, similarto what was illustrated in FIGS. 7A-7C. A center ground cutting edge2032 is what is illustrated in FIGS. 17A-17G. This edge may be ground,and may have a local radius of curvature that is <0.010 inch, or <0.002inch, or generally may be as sharp as possible,

In an embodiment, it also is possible, referring now to FIG. 17G, thatsome portion of the distal end or tip of the guidance region 2015 couldbe sharpened and could be suitable for cutting. Such sharpening couldallow a surgeon to perform at least some cutting using the distal tip ofscoring blade 2010, without removing blades 2010 from the power tool andreplacing them. The tip may be ground to a sharp edge similarly to whatis illustrated in FIGS. 7A-7C. The local shape of the sharpened regioncould be any desired shape. The distal edge of the sharpened region isillustrated in FIG. 17G as having a short straight segment, but moregenerally any shape is possible. This edge may be ground, and may have alocal radius of curvature that is <0.010 inch, or <0.002 inch, orgenerally may be as sharp as possible, In the blade of FIG. 17G, it canbe seen that, proceeding around the perimeter, there is a cutting edge2032, followed by a non-cutting edge which is guidance edge 2016,followed by a sharp feature or edge at the tip of guidance region 2015,followed by a non-cutting edge which is guidance edge 2016, followed bya cutting edge 2032.

In embodiments, the blade 2010 may have dimensions appropriate forfitting inside typical dimensions of an intramedullary canal thatcontains bone cement needing to be removed during revision surgery. Forexample, the width dimension of the body 2030 may be in the range of 0.2inch to 1.0 inch. The length of the body 2030 may be in the range of 1.0inch to 18 inch. The blade 2010 may comprise metal such as stainlesssteel and may have a thickness suitable so that the blade 2010 canwithstand a compressive or impact force along the proximal-distaldirection of at least 10 N without buckling, or at least 50 N.

Surgical Method

An embodiment of the invention can also comprise a method of removingbone cement from the wall of an intramedullary canal at a revision site,using the various blades described herein. The method may comprise twosteps, with the first step being scoring the bone cement using an axialscoring blade 2010, and the second step being removing bone cement usinga blade such as the Cement Removal Blade 10.

Axial scoring blade 2010 may be used in the first step. By making theseaxial cuts through at least some of the depth of the bone cement, thestrength of the bone cement layer is reduced significantly, and the bonecement may be sectioned into axial strips that can then be very quicklychipped away with the CRB 10, creating large chips of bone cement andalso exposing a bone surface that is clean and well preserved. These aretwo very desirable outcomes. Currently, removing bone cement during arevision surgery is a time-consuming and difficult step. Leaving a cleanbone surface without gouges and chips, one where the bone is wellpreserved, will maintain the structure and strength of the bone andprovide a favorable surface for attachment of a new implant.Furthermore, reducing the duration of surgery is always beneficial forthe patient.

In an embodiment, the Scoring Blade 2010 may be used with theVersaDriver™ pneumatic osteotome as disclosed in U.S Pat. ApplicationSerial No.17/402,511 and U.S. Pat. Application Serial No.63/066,089.Alternatively, the described scoring blade 2010 could be driven by anyautomated or manual type osteotome system, or it could be used by itselfas a manual osteotome driven by a hammer or mallet.

The scoring step may then be followed by using a CRB blade 10 asdisclosed herein, or by cutting using any other type of blade. It isbelieved that the process of removing bone cement from bone may besignificantly improved by use of the Scoring Blade 2010 in a process asdescribed herein.

Reference is now made to FIGS. 18A-18C. In FIGS. 18A-18C, for simplicityof illustration, the bone cement is shown as being an annulus of uniformthickness, and the bone is also shown as being an annulus. FIG. 18Ashows the scoring blade 2010 in position with respect to a cut end of anintramedullary canal at the beginning of a scoring cut. This is shownwith other scoring cuts having already been made at other angularlocations around the same intramedullary canal.

FIG. 18B shows the same blade 2010 making the same scoring cut, but withthe blade 2010 located deeper in the intramedullary canal with a portionof the scoring cut completed. FIG. 18C is a cutaway version of FIG. 18B.

In an embodiment of the method, the scoring blade 2010 may be used tocreate one or more axial scoring cuts along the surface of the bonecement that covers the bone. Typically, this scoring cut may beperformed on the bone cement surface that lines the intramedullary canalafter an implant has been removed during revision surgery. As thecutting procedure progresses, the scoring blade 2010 may advance and theregion of undisturbed bone cement may recede.

Typically, the bone cement present at the start of a revision surgerymay be of varying thickness, varying as a function of either or both theposition along the long direction of the intramedullary canal and theangular position around the perimeter of the intramedullary canal.

During use, the guidance edge 2016 of the blade 2010 may be positionedso as to bear against the bone cement that is more distal with respectto the area that is to be cut by the cutting edge of the blade 2010. Thenot-yet cut bone cement may provide a natural depth guide for the blade2010 so that the blade 2010 does not cut deeper than the Notch Width.The scoring cut may have a cut width and a cut depth. In embodiments,the cut width of the scoring cut may be approximately equal to (orslightly greater than) the thickness of the scoring blade 2010. Thedepth of the scoring cut in the bone cement or other material depth maybe approximately equal to the notch dimension or inset distance (W, W1,W2 in FIGS. 17E-17F) of the blade 2010, due to the functioning of theguidance edge 2016 as a follower along the surface of the undisturbedbone cement or other material.

In regard to the depth of the scoring cut and the dimensions of theScoring Blade 2010, Scoring Blades 2010 of various notch widths can beprovided to accommodate different local thicknesses of bone cement.Scoring blades 2010 can be swapped out of the powered tool in order tochange the depth of the scoring cut. Also in this regard, anon-symmetric scoring blade 2010 as described herein can be used, suchthat the depth of scoring cut can be varied by cutting with one side orcutting edge of the blade 2010 rather than the other side or cuttingedge of the blade 2010, simply by changing the orientation of the powertool.

Of course, it is possible to use the scoring blade 2010 to cut throughsubstantially the entire or exact thickness of the bone cement on theinternal surface of the intramedullary canal. However, typical surgicalconditions are such that the thickness of bone cement might vary fromone location to another, the bone cement might not be fully visible tothe surgeon, it might not be possible to exactly ascertain the bonecement thickness or match the cut depth to the local thickness of bonecement, and it is desirable to perform surgery with reasonable speed. Inview of considerations such as these, it is believed that, even if it isnot possible to exactly match the cutting depth to the local bone cementthickness, it is helpful if axial scoring is performed such that thecutting depth is at least approximately 50% of the local bone cementthickness. It is believed that scoring to this extent will sufficientlyweaken the strength of the bone cement cylinder lining the bone canal sothat a follow-on blade such as the Cement Removal Blade 10 can do itswork more efficiently than would occur in the absence of axial scoringof the bone cement. In FIGS. 18A-19B, it is illustrated that the scoringblade 2010 cuts through some of the thickness, but not the entirethickness, of the bone cement, thereby avoiding the possibility ofcutting into the bone itself. It is believed that it is preferable tocut a scoring cut through a portion of the bone cement while leaving alittle bit of the bone cement unscored, rather than cutting so deeply asto score some of the bone itself. Typically, the scoring operation wouldonly be a preparatory step, anyway, in preparation for a more completecement removal using a different blade such as blade 10 describedelsewhere herein.

In regard to the spacing between adjacent axial scoring cuts, it isbelieved that, up to a reasonable number of axial scoring cuts, the moreaxial scoring cuts are created in the bone cement, the easier and morereadily the bone cement is able to be removed. It is believed to bedesirable for the distance between the axial scoring cuts to be roughlyequal to the width of the tip or body of the CRB blade 10, or not morethan two times the width of the tip or body of the CRB blade 10.

In still other embodiments, the axial scoring cuts can be achieved byother means such as small saws, files, osteotomes, sagittal saws, finetoothed rasps, or other cutting instruments capable of creating axialcuts through bone cement. Such cuts can be made either under poweredmotion from a power tool or by the use of tools by hand or with handdriving means such as hammers or mallets.

FIGS. 18A-18C show a CRB 10 cutting bone cement that remains between thescoring cuts. FIG. 18A shows the axial scoring blade 2010 in position atthe end of the intramedullary canal, at the beginning of the process ofmaking a scoring cut. It can be noted that in FIG. 18A, other scoringcuts have already been made at other angular positions around theintramedullary canal. FIG. 18B shows the same blade but deeper in theintramedullary canal partway through the process of making that scoringcut. FIG. 18C is a sectioned view of FIG. 18B.

After the axial scoring cuts are made with the Scoring Blade 2010, ablade such as the blade 10 described elsewhere herein may be used tochip away at the bone cement that remains between the axial scoringcuts, as well as chip away at any bone cement that may remain at theaxial scoring cuts if the axial scoring cuts do not penetrate throughthe bone cement all the way to the bone. It is believed that after thefirst amount of bone cement in between one or more axial scoring cuts isremoved, the process of breaking up or cutting or removing the remainingbone cement should become significantly easier. This is shown in FIGS.20A-20B. FIG. 19A shows Cement Removal Blade 10 in the process ofcutting a region of bone cement that is located between two adjacentscore cuts. As illustrated, the width of the body 30 or tip 20 of blade10 is approximately equal to the distance between adjacent score cuts.FIG. 19B is a sectional view of FIG. 19A.

Embodiments

Embodiments of the invention are further described but are in no waylimited by the following embodiments:

Embodiment 1. A blade for use in cutting, said blade comprising:

-   a guidance portion;-   a cutting portion that is continuous with said guidance portion;-   a transition portion that is continuous with said cutting portion;    and-   a gripping portion that is continuous with said transition portion,-   wherein said blade has a longitudinal axis,-   wherein said cutting portion is planar having a cutting portion    planar surface facing in an upward direction and has at least one    cutting edge that is adapted for cutting,-   wherein said gripping portion has an upward-facing surface facing    generally in said upward direction and said upward-facing surface    does not entirely lie in a single plane, and-   wherein said transition portion has a three-dimensional surface    transitioning between said cutting portion and said gripping    portion,-   wherein said guidance portion comprises edges that are less sharp    than said cutting edge of said cutting portion.

Embodiment 2. The blade of embodiment 1, wherein said guidance portionedges have a local radius of curvature that is larger than 0.002 inch.

Embodiment 3. The blade of embodiment 1, wherein one of said guidanceportion edges is generally straight and parallel to said longitudinalaxis, said straight edge being less sharp than said cutting edge of saidcutting portion of said blade.

Embodiment 4. The blade of embodiment 1, wherein said guidance portionhas a distal-most end that, when viewed from said upward direction, isconvex having a radius of curvature of at least one-tenth of aside-to-side dimension of said guidance portion.

Embodiment 5. The blade of embodiment 1, wherein said guidance portionhas a distal-most end having radius of curvature greater than 0.002inch.

Embodiment 6. The blade of embodiment 1, wherein said guidance portionhas a distal-most end that is ground to a cutting edge having a radiusof curvature less than 0.010 inch.

Embodiment 7. The blade of embodiment 1, wherein said guidance portionhas a side-to-side dimension smaller than a side-to-side dimension ofsaid cutting portion.

Embodiment 8. The blade of embodiment 1, wherein, where said guidanceportion meets said cutting portion, an inset distance on one side ofsaid blade is different from an inset distance on an opposed side ofsaid blade.

Embodiment 9. The blade of embodiment 1, wherein said cutting portioncomprises a cutting surface and said cutting surface is top-ground,bottom-ground, center-ground, or ground to a sharp edge that is locatedbetween opposed surfaces of said cutting portion.

Embodiment 10. The blade of embodiment 1, wherein said cutting surfaceangle is forward-facing, forming an acute angle of less than 90 degreeswith respect to a longitudinal axis of said guidance portion.

Embodiment 11. The blade of embodiment 1, wherein said cutting surfaceangle is perpendicular to said longitudinal direction, or isrearward-facing.

Embodiment 12. The blade of embodiment 1, wherein said gripping portionis suitable to be gripped in a power tool.

Embodiment 13. The blade of embodiment 1, wherein said gripping portionis suitable to be struck by a hammer.

Embodiment 14. A method of removing bone cement from an internal surfaceof an intramedullary canal, said method comprising:

-   cutting an axial score cut in said bone cement, said axial score cut    having a cut width and a cut depth, while leaving an undisturbed    region of said bone cement adjacent to said score cut; and-   cutting said undisturbed region of said bone cement adjacent to said    score cut.

Embodiment 15. The method of embodiment 14, wherein said cutting saidaxial score cut and said cutting said undisturbed region are performedusing different cutting blades.

Embodiment 16. The method of embodiment 14, wherein said cutting saidaxial score cut is performed using a blade that comprises a guidanceportion, a cutting portion that is continuous with said guidanceportion; a transition portion that is continuous with said cuttingportion, and a gripping portion that is continuous with said transitionportion.

Embodiment 17. The method of embodiment 14, wherein said cutting saidaxial score comprises cutting to a depth of at least half of a localthickness of said bone cement.

Embodiment 18. The method of embodiment 14, wherein said cutting saidaxial score comprises cutting to a depth less than a local thickness ofsaid bone cement.

Embodiment 19. The method of embodiment 14, further comprising cuttingan undisturbed region of said bone cement that is located deeper withinsaid bone cement than a bottom of said score cut.

Embodiment 20: The method of embodiment 14, wherein said methodcomprises cutting a plurality of said score cuts, wherein adjacent onesof said score cuts are separated from each other by a distance that isbetween one and two times a width of a tip or body of a blade used tocut said undisturbed region of said bone cement.

Embodiment 21. The method of embodiment 14, wherein said cutting saidundisturbed region is performed using a blade that comprises:

-   a tip, said tip having a tip thickness measured perpendicular to a    local surface of said blade; and-   a body, proceeding proximally from said tip, said body having a body    width dimension;-   wherein said body and said tip both extend generally along a    proximal-distal direction,-   wherein said tip is trough-shaped having a tip concave surface and    an opposed tip convex surface,-   wherein said tip has a tip cross-section, taken perpendicular to    said proximal-distal direction,-   wherein, said tip cross-section has a concave surface that has, at    some location, a tip internal radius of curvature that is a smallest    radius of curvature of said concave surface,-   wherein said tip cross-section can be enveloped by a minimum tip    enveloping rectangle that is a smallest rectangle that can enclose    said tip cross-section,-   wherein said minimum tip enveloping rectangle has a tip section    width dimension and a tip section height dimension and has a tip    aspect ratio that is a ratio of said tip section width dimension to    said tip section height dimension,-   wherein said tip aspect ratio ranges from 1.0 to 3.5,-   wherein said tip internal radius of curvature is between 2% and 40%    of said body width dimension,-   wherein said tip internal radius of curvature is approximately 0.05    to 6.25 times said tip thickness,-   wherein when viewed from above said concave surface, said tip has a    swept-back configuration, and-   wherein said tip has a distal edge having a suitable sharpness and    hardness to cut a material of interest.

Further Comments

The blade of embodiments of the invention has been designed, first andforemost, to provide control to the surgeon so the blade is alwaysmoving where the surgeon wants it to go. The blade is designed so thesurgeon can easily control the direction of cut and the depth of cut. Ingeneral, there tends to be a tradeoff between cutting speed and cuttingcontrol. The faster the cutting speed, the less control the surgeon hasof the blade. It is possible that faster cutting blade designs caneasily veer away from the intended line of cut or cut deeper thanexpected into the bone cement. If the blade is designed so that thecutting speed is significantly reduced, then the blade will cut tooslowly to be effective, or will not cut at all. Finding a balance or“sweet spot” between blade control and cutting speed is the goal we seekin varying the different design parameters of the blade. We want to givethe surgeon excellent control over the blade so that the surgeon canfeel confident in not injuring the patient, while also providingsufficient cutting speed so the surgeon finds the blade to be much moreeffective at removing bone cement than using a hammer and chisel.

In embodiments of the invention, the powered handpiece can be powered bypneumatics or by electricity. Examples of a powered pneumatic handpieceare Palix Medical’s VersaDriver™ (described in U.S. SerialNo.63/066,089, filed Aug. 14, 2020 and U.S. Serial No.17/402,511, filedAug. 14, 2021) and Exactech’s Acudriver®. An example of an electricallypowered handpiece is DePuy Synthes’ Kincise™.

The blade can be made from any strong material or combination ofmaterials that can withstand the compressive or impact forces of thecutting action, along the proximal-distal direction of the blade 10,while maintaining a sharp cutting edge. Blade 10 may in general be madeof a metal that is suitable for use in a surgical setting. Some examplesare 300 and 400 series stainless steels, carbon fiber, ceramic, nickeltitanium, etc. The blade, or in particular its cutting edge, may have ahardness greater than HRC 35. If present, a splash guard may be made ofa polymer such as plastic or rubber. The chuck of the powered drivingdevice, if present, may generally be made of a suitable metal, althoughother materials are also possible.

In an embodiment of the invention, the blade 10 may be formed startingwith flat material and then deforming the flat material by bending,stamping etc.

In an embodiment of the invention, the cutting edge may be formed bygrinding, or by other appropriate technique. The blade 10 could also bemade by many other processes including forging, 3D printing, CNCmachining, injection molding, or welding of two or more pieces of metal.

The grinding process can be performed by creating a three-dimensionalprofile on the face of a grinding wheel that matches thethree-dimensional profile of the blade tip 20, so that when the grindingwheel contacts the blade it grinds the cutting edge evenly on all facesat the same time. The grinding wheel can then be moved relative to theblade, or the blade relative to the wheel, axially along a plane whichcreates an angle, equal to the Bevel Edge Angle “E”, with the planetangent to the convex portion of the blade tip. This will create aconsistent Bevel Edge angle equal to angle “E” across the blade tip. Analternative means of grinding the blade tips is to use a CNC grinder orrobotically controlled grinder that is able to produce grindingcontours, allowing the grinding wheel to produce consistent Bevel EdgeAngles.

It is also possible that a similar blade design could be used in amanual process with a hammer. If intended for manual use with a hammer,the blade could be provided with an impact surface for the hammer tostrike, such as a handle. However, if used manually with a hammer, itcould be expected that the speed of cut and ease of use would be lessthan the results with a powered handpiece.

It is further possible that edges of the tip 20 could be serrated.

Although the body of the blade is shown as being generally straightalong the longitudinal direction of the body of the blade, it is alsopossible that, for a particular surgical situation, the body of theblade could be made with a shape, along its longitudinal direction, thatis something other than straight, as shown in FIG. 15A and FIG. 15B.

It is also possible for the tip 20 to be along a different directionfrom the body 30, as can be seen in FIG. 16 . The angle theta could be+/- 10 degrees offset from the direction of the body 30.

In the various illustrations, the trough shaped cross-sections of thebody and of the hub have been shown as having equal legs on each side ofthe longitudinal axis or plane of symmetry of the blade. However, itwould also be possible that these legs could be unequal if desired. Insuch a situation, the minimum tip enveloping rectangle, or the minimumbody enveloping rectangle, can simply be the smallest rectangle that canenclose the cross-section of the tip or body, even if the section is notfully symmetric.

Although embodiments of the invention have been described with respectto cutting bone cement, embodiments could also be used for cutting othermaterial instead of or in addition to bone cement.

In general, any combination of disclosed features, components andmethods described herein, that is physically possible, is intended to bewithin the scope of the claims.

All cited references are incorporated by reference herein.

Although embodiments have been disclosed, it is not desired to belimited thereby. Rather, the scope should be determined only by theappended claims.

What is claimed is:
 1. A scoring blade for scoring bone cement to beremoved from an intermedullary canal of a bone, the scoring bladecomprising: a longitudinal body having a proximal end and a distal end,and defining a longitudinal axis extending between the proximal end andthe distal end; a guidance region at the distal end, the guidance regioncomprising at least one guidance edge extending generally parallel withthe longitudinal axis; and a cutting region between the guidance regionand the proximal end, the cutting region comprising at least one cuttingedge having a width extending outwardly from the guidance edge at anangle relative to the longitudinal axis.
 2. The scoring blade of claim1, wherein the angle of the at least one cutting edge relative to thelongitudinal axis is less than 90 degrees.
 3. The scoring blade of claim1, wherein the angle of the at least one cutting edge relative to thelongitudinal axis is about 90 degrees.
 4. The scoring blade of claim 1,wherein the width of the at least one cutting edge is between 1 mm to 6mm.
 5. The scoring blade of claim 1, wherein the at least one cuttingedge is formed by a notch between the cutting region and the guidanceregion.
 6. The scoring blade of claim 1, wherein the at least onecutting edge comprises a first cutting edge having a first widthextending outwardly in a first direction from a first guidance edge ofthe guidance region, and a second cutting edge having a second widthextending outwardly in a generally opposite second direction from asecond guidance edge of the guidance region.
 7. The scoring blade ofclaim 6, wherein the first width and the second width are generallyequal.
 8. The scoring blade of claim 6, wherein the first width isgreater than the second width.
 9. The scoring blade of claim 1, furthercomprising a hub at the proximal end configured for engagement with atool.
 10. The scoring blade of claim 9, wherein the hub is non-planar.11. The scoring blade of claim 10, wherein the hub is generally V-shapedin cross-section.
 12. The scoring blade of claim 11, further comprisinga transition portion between the hub and the cutting portion, thetransition portion defining smoothly curving transition surfacestransitioning between a non-planar profile toward the hub and agenerally flat profile toward the cutting portion.
 13. The scoring bladeof claim 9, in combination with a tool having a chuck configured forcoupling engagement with the hub.
 14. The scoring blade of claim 13,wherein the tool is a power-driven tool.
 15. The scoring blade of claim1, having a substantially constant blade thickness throughout the entirelongitudinal body from the proximal end to the distal end.
 16. Thescoring blade of claim 15, wherein the scoring blade is manufacturedfrom a constant-thickness sheet material and formed by stamping orbending.
 17. The scoring blade of claim 1, wherein the guidance regioncomprises a rounded portion not adapted for cutting and having a radiusof curvature greater than 0.002 inch.
 18. The scoring blade of claim 1,wherein at least a portion of a distal tip of the guidance regioncomprises a sharpened edge.
 19. A scoring blade for scoring bone cementto be removed from an intermedullary canal of a bone, the scoring bladecomprising: a longitudinal body having a proximal end and a distal end,and defining a longitudinal axis extending between the proximal end andthe distal end; a guidance region at the distal end, the guidance regioncomprising a rounded distal tip and first and second guidance edgesextending generally parallel to the longitudinal axis; and a cuttingregion between the guidance region and the proximal end, the cuttingregion comprising a first cutting edge having a first width extendingoutwardly from the first guidance edge at a first angle relative to thelongitudinal axis, and a second cutting edge having a second widthextending outwardly from the second guidance edge at a second anglerelative to the longitudinal axis.
 20. The scoring blade of claim 19,wherein the first width and the second width are generally equal. 21.The scoring blade of claim 19, wherein the first width is greater thanthe second width.
 22. The scoring blade of claim 19, wherein at leastone of the first and second angles is less than 90 degrees.
 23. Thescoring blade of claim 19, wherein at least one of the first and secondangles is about 90 degrees.
 24. The scoring blade of claim 19, whereinthe first and second widths are between 1 mm to 6 mm.
 25. The scoringblade of claim 19, wherein the first and second cutting edges are formedby a notch between the cutting region and the guidance region.
 26. Thescoring blade of claim 19, further comprising a hub at the proximal endconfigured for engagement with a tool.
 27. The scoring blade of claim26, wherein the hub is non-planar.
 28. The scoring blade of claim 27,wherein the hub is generally V-shaped in cross-section.
 29. The scoringblade of claim 27, further comprising a transition portion between thehub and the cutting portion, the transition portion defining smoothlycurving transition surfaces transitioning between a non-planar profiletoward the hub and a generally flat profile toward the cutting portion.30. The scoring blade of claim 26, in combination with a tool having achuck configured for coupling engagement with the hub.
 31. The scoringblade of claim 30, wherein the tool is a power-driven tool.
 32. Thescoring blade of claim 19, having a substantially constant bladethickness throughout the entire longitudinal body from the proximal endto the distal end.
 33. The scoring blade of claim 32, wherein thescoring blade is manufactured from a constant-thickness sheet materialand formed by stamping or bending.
 34. The scoring blade of claim 19,wherein at least a portion of the distal tip of the guidance regioncomprises a sharpened edge.
 35. A system for scoring bone cement to beremoved from an intermedullary canal of a bone, the system comprising: ascoring blade for scoring bone cement to be removed from anintermedullary canal of a bone, the scoring blade comprising: alongitudinal body having a proximal end and a distal end, and defining alongitudinal axis extending between the proximal end and the distal end;a guidance region at the distal end, the guidance region comprising atleast one guidance edge extending generally parallel with thelongitudinal axis; a cutting region between the guidance region and theproximal end, the cutting region comprising at least one cutting edgehaving a width extending outwardly from the guidance edge at an anglerelative to the longitudinal axis; and a hub at the proximal end; and atool having a chuck configured for coupling engagement with the hub. 36.The system of claim 35, wherein the tool comprises a powered tool. 37.The system of claim 35, wherein the tool comprises a manually driventool.
 38. The system of claim 35, further comprising a cement removalblade, and wherein the chuck of the tool is configured forinterchangeable engagement with the scoring blade and the cement removalblade.
 39. A surgical method of removing bone cement from anintermedullary canal of a bone, the method comprising: scoring the bonecement by making a plurality of axial scoring cuts through at least aportion of the depth of the bone cement within the intermedullary canalof the bone using a scoring blade; and removing the scored bone cementfrom the intermedullary canal of the bone using a cement removal blade.